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Making the decision to take insulin to control your diabetes can be a big and scary decision. No one wants to give themselves a shot. It’s inconvenient. It can make you hungry. It can make your blood sugar go low. It can cause weight gain. No one likes to be around needles.

While these beliefs are true, there’s so much more to taking insulin. For some, it’s the key to controlling blood sugar. It can bring your numbers closer to a normal range than any amount of diet or exercise can. It can be just what you need to stop the fatigue and constant trips to the bathroom! Insulin can make the difference in how long you live and what quality of life you enjoy. But….there are so many decisions!

My doctor gave me the choice between using an insulin pen or a vial. Which is the best insulin injection device?

Vials have been around for a very long time, so we’ll talk about those first. Most of us have seen a vial before. You know, the small glass bottle with a rubber cover over the top.

  • Number of units –  Insulin vials are standard in size. Most vials of insulin contain 100 units/ml of solution in a 10 ml vial. So how many units of insulin are in a standard vial?  1000 units. Some examples of these include Lantus, Levemir, Humalog, Novolog, 70/30, ReliOn R and ReliOn N.
  • Cost – The cost of a vial of insulin will absolutely depend on what kind of insulin is in the vial.  But when we look at the cost per unit of insulin, the cost of vials vs. pens is about the same.  For example, the cash price for a vial of Lantus is approximately $300 for 1000 units, which equals 30 cents per unit. The cash price for a box of pens is approximately $450 for 1500 units (see pen information), which is also equal to 30 cents per unit.

Insulin Syringes

When a prescription for a vial is written, you should also get a prescription for syringes. Is the prescription totally necessary for syringes? No, it is not. Syringes are available behind the counter at the pharmacy. However, if you are trying to get your insurance to pay for it, you will need a prescription.

How do I know which syringe to choose?

Syringes vary in 3 ways – size, gauge, and length.

  • Syringe size – This refers to how much insulin a syringe will hold.  Insulin syringes can either contain 30, 50 or 100 units each. Does the syringe size matter? No, as long as you can see the markings and your dose can fit into that syringe. If you are taking 60 units of Levemir, you’ll only use the 100 unit syringe. The 100 unit syringe is marked in increments of 2, while the 30 and 50 unit syringes are marked by 1’s.
  • Syringe length – The needles are either considered short or long. Short needles are typically 6 mm or 8 mm. The short needles may also be labeled as 5/16″. Long needles are 12.7 mm, which is equal to ½ inch. These are rarely needed, even if you are a bit fluffier around the middle.
  • Syringe gauge – The gauge refers to how thick a needle is. The higher the number, the thinner the needle…and less painful. Syringe needles are commonly 28-31 gauge. Your prescriber may suggest a specific syringe size, but it’s really your decision on what size to try.

Cost – Syringes are sold in packages of 10 or boxes of 100. The prices vary, but a ballpark cost is $25-$40 for a box of 100. Syringes are made by both brand name and off-brand companies.  Either is acceptable to use and there should be no difference in quality.

Injection technique – Vials and syringes are a bit more involved than pens and pen needles. In order to get the insulin to be easily drawn up into the syringe, you must first inject air into the vial.  The basic technique is to draw air into the syringe equal to the number of units to be injected. With the vial upright on a table, insert the needle through the rubber cap and push the plunger down to force the air into the vial.  Without removing the syringe, turn the vial upside down and draw up the amount of insulin needed.  This can then be injected according to your prescriber’s instructions. Your prescriber’s office or pharmacy can also demonstrate how to do this.

Insulin Pens and Pen Needles


There really isn’t a best insulin pen. The name of the pen will vary with the type of insulin it contains. For example, Lantus pens are called SoloStar.  Levemir pens are called either FlexPen or FlexTouch. Humalog pens are called KwikPen. While these names are meant to be specific to each type of insulin, they can also create confusion!

  • Number of units – Remember that the concentration of most insulin is 100 units/mL (exceptions do exist!). Many pens are 3 mL in size, meaning they contain 300 units.  Pens can be sold individually, or more commonly, in a box set of 5 pens.  A box of pens will contain 1500 units of insulin.  To review – 1 pen contains 300 units, 5 pens in a box, so 1 box contains 1500 units. The confusing part comes in when the insulin is more concentrated than 100 units/mL, but we’ll stick with normal concentration for our discussion here.
  • Cost – When paying a cash price, pens are more expensive than vials…BUT that’s because you get more insulin with each prescription. That’s 1500 units per prescription. (Remember that vials contain 1000 units.) We stated earlier that the cost per unit is essentially the same.  For insurance co-pay purposes, the copays may be the same for a monthly supply of either vials or pens,  but this could end up making pens less expensive than vials because a larger quantity of insulin is dispensed (1500 units vs 1000 units).

Insulin Pen needles

Pens don’t come with pen needles. Just like syringes, they must be purchased separately.

How do I know which pen needle to choose?

Pen needles vary in gauge and length, similar to syringes. When staring at all of the pen needle options at a pharmacy or online, choosing the best insulin pen needle size for you can seem overwhelming.  We’ll simplify that process here.

  • Length – Pen needles vary in length, ranging from 4mm (tiny) to 12mm.  The 4mm or 6mm work well for most people.
  • Gauge – Pen needles are ususally either 31G or 32G.

Just like syringes, it doesn’t matter what size you use. I recommend starting with the smallest size first. You just need the needle to make it through the skin to the tissue just on the other side. Most people do well with the shorter lengths.

Cost – Pen needles are sold in boxes of 100. The cost can range from about $15 -$45 for a box, but these may also be covered by insurance with a prescription.

Bottom Line Recommendation for the Best Insulin Injection Device

Insulin pens and pen needles are definitely easier to use than vials and syringes. They have the added convenience of being small and portable and don’t require the extra step of injecting air and drawing up the insulin. With pens, you simply dial up to the dose you need. You can even dial back down if you go past your target dose.  The downside? They are more expensive if you are paying cash.

Are there any advantages of vials and syringes over pens? There may be a few. They are a little bit cheaper. If you happen to be one who mixes two types of insulin together, you can only to that with vials. Of course, many of the newer insulins are not approved for mixing, but the older NPH and Regular can still be mixed. Another benefit is if you (or someone you know taking insulin) can’t see very well, you can get someone else to draw up several syringes at a time and leave them in the refrigerator for use when a caregiver isn’t present. This can’t be done with pens.

Starting insulin can be an intimidating process. Learning all about storage, monitoring and dosing can be overwhelming enough…without having to make decisions about pens and vials. Take things slowly. Try out one option of pen or vial and syringe size. Change it up next month if you’d like. As long as the right dose of insulin goes into your body, the specifics aren’t as important. You can do this!


What type of insulin device do you prefer? What are you confused about?   What questions do you have about insulin?

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